Presently various fluids are used for heat transfer. The suitability of the heat-transfer fluid depends upon the application process. For example, some electronic applications require a heat-transfer fluid which is inert, has a high dielectric strength, has low toxicity, good environmental properties, and good heat transfer properties over a wide temperature range. Other applications require precise temperature control and thus the heat-transfer fluid is required to be a single phase over the entire process temperature range and the heat-transfer fluid properties are required to be predictable, i.e., the composition remains relatively constant so that the viscosity, boiling point, etc. can be predicted so that a precise temperature can be maintained and so that the equipment can be appropriately designed.
Perfluorocarbons, perfluoropolyethers (PFPEs), and some hydrofluoroethers have been used for heat-transfer. Perfluorocarbons (PFCs) can have high dielectric strength and high resistivity. PFCs can be non-flammable and are generally mechanically compatible with materials of construction, exhibiting limited solvency. Additionally, PFCs generally exhibit low toxicity and good operator friendliness. PFCs can be manufactured in such a way as to yield a product that has a narrow molecular weight distribution. PFCs and PFPEs can exhibit one important disadvantage, however, and that is long environmental persistence which can give rise to high global warming potentials.
Perfluoropolyethers (PFPEs) exhibit many of the same advantageous attributes described for PFCs. In addition, the methods developed for manufacturing these materials can yield products that are not of consistent molecular weight and thus can be subject to performance variability.